Which is most clearly a topic sentence? Some intriguing, though incomplete, ideas have come from researchers trying to explain why our brains give us such vivid and emotional experiences every night. Sigmund Freud believed that
dreams are expressions of memories and anxieties that we avoid thinking about during our waking lives. Carl Jung provided a modern version of the ancient opinion that dreams are messages that help us figure out how to avoid disaster, almost like prophecies. Perhaps the
popularity of Jung's interpretation is the reason that many people keep
dream journals, wherein they write down their dream experiences
before they forget them. After all, if dreams are messages, one had
better not ignore them

A. Sigmund Freud believed that dreams are expressions of memories
and anxieties that we avoid thinking about during our waking lives.

B. After all, if dreams are messages, one had better not ignore them.

C. Perhaps the popularity of Jung's interpretation is the reason that
many people keep dream journals, wherein they write down their
dream experiences before they forget them.

D. Some intriguing, though incomplete, ideas have come from
researchers trying to explain why our brains give us such vivid and
emotional experiences every night,